Here is a better summary of where I'm at with my project.
The source is an email to the TCRG list -

>Bruce wrote:

> ps -- Rob, how is Robocities coming along? If you need
some help, the
> group is ready to step up and provide whatever you
need. Right group
:?)
>

Robocities is making me cry. Major engineering hurdles,
no time. Maybe the group could take my wife and kids for
a few weeks? :-)

Seriously folks -

Bruce I'm looking at constructing not so much a city but a
ziggurat, kind of like a square tower of Babel out of pink
foamular(tm) insulation foam (how strange is that).
Unfortunately planning out an entire city would be just
too hard for a protocity, so if this structure is too
weird for the Science Museum, hey I understand.

What I'll need is a 11' x 11' space, about 11' high. I'll
need another 10' x 10' space to put the pre-build
material. These dimensions can be scaled down as needed.

What we're looking at, with as many corners cut as I could
manage, is 4 robots; 1 to place bricks, 1 to deliver
bricks, 1 to deliver roof/floor tiles, 1 to deliver
ramps. The walls will be 16" high making each level 17"
high with the tiles. The roof tiles are approximately 32"
x 32", the individual bricks are 8" x 4" x 8". 7 levels
total with a 32" x 32" spot on the top of the building for
the robots to sit when the structure is complete. The
walls will actually be laid as "hallways" or "tunnels"
that run through the structure; I currently have no plan
for building a closing wall around these tunnels so you'll
be able to see through the ziggurat structure.

Engineering hurdles-

The whole system is based on the brick laying robot
because that is the robot that will move the least. One
challenge was to determine if this robot would give
direction, or if a computer would control the show. Having
the robot give direction to the other robots was really
attractive because then I wouldn't have to program any
other systems like a computer. But, because I have some
calibration considerations and yet I don't want to lug a
computer around, I've decided to program a PDA to do the
decision making in an extremely centralized method. I
expect to change this in future upgrades (famous last
words).

I'm trying to create an initial system with the least
complexity possible to insure completion by the deadline.
This means I'll be doing a lot of experimenting in the
future weeks and then adding hardware/software as needed.
For example initially I want to see if dead-reckoning is
enough to get the protocity built, then I'll add an
accelerometer, compass, etc. What I don't want to do is
add stuff that I think I'll need and increasing the
complexity.

Mechanically, I finally built the arm design I like the
most for the brick layer, wired up the base, and I'm
adding sensors and getting ready to program. This is the
first robot, but don't panic yet (let me do the panicking
here), this is the hard one, the other three robots will
be significantly easier to build and program after this
one is done.

Another problem is preparing the bricks and the tiles, and
how to configure them as pre-build material that's
accessible to the robots. This will probably be the last
thing I work on, which means this is probably the thing
that's going to get skipped and I get to hand my robots
material by hand (bummer). Oh and I doubt the robots will
have enough battery power to complete the structure, so
I'll need to swap out the batteries without having the
system lose it's place. Charging the robots is currently
not an option since this will increase the complexity.

Rapid-Prototyping Boards have been a really big help, but
there are still some flaws that are being worked out like
my motor drivers stack on the motor interface board poorly.

Lastly, I was just relating to Jeff Sampson earlier that I
don't think I've ever completed a robotics project to this
degree, so some funny stuff is coming up like what
software component to program first.

To sum it up - overall I would say I'm about 6 months
behind but progressing nicely.

OK, 1 month to go to meet the St. Paul Science
Museum/Shapiro deadline for having my robots build the
first proto - robocity. I've been working like a phene,
but chances are I'm not going to meet the Nov 8th
deadline. Right now I'm about a month behind and I really
didn't understand how much infrastructure had to be in
place - it's amazing. I could put 2 or 3 guys to work and
still not make it.

But that is neither here nor there, I've got a month,
I've found an arm design I like for the first robot so
I've started throwing the electronics together and
programming it. I've got a real good idea of what needs
to be done and what corners to cut. and the game ain't
over.

So I've been soldering boards for the last month and I'm
about 85-90% done.
Here's a picture (See the 9/03/2003 picture on the
right). OK, I might have taken a little-bit
of time and upgraded my computer system to 2.4GHz P4 on an
800 MHz bus with 1Gig of RAM, 6 - USB 2.0 ports and an
Ethernet port on board, a 7200 RPM 160Gig HD, DVD Rom
Burner, WinTV, Windows and Office XP professional (yes, I
$upport the empire), etc. - I kept my Matrox video card
with the dual monitors. I'm pretty happy with it. Now
understand, I didn't WANT to build this computer system, I
HAD to build it - to support the robotics GUI for the
Robocities ;-).

Speaking of Robocities - this month I want to get
the
first set of city-building robots done and build the first
proto-city. I also have to test all boards I've put
together. My goal is to have something to show for our
next TCRG robotics meeting.

First of all, I brought the mechanically completed (no
brain yet) bricklayer to my
July TCRG robot meeting. It looks like I'll have to
redesign the arm extension, but this design works pretty
well. The Robocities concept is still a go.

The boards are done and on their way from Bulgaria. I
just
ordered all the parts for the boards, and all the motors I
think I'll need. The only kicker is that one of the parts -
the accelerometer, isn't due to ship until 3 days before
I'm suppose to have this project finished and tested, so
that's no good.

I've got some little sub projects, like making a brass
cutter and an Acrylic cutter that I want to build before I
build the next onslaught of robots. This sounds like a
distraction, but one of my objectives for this project is
to create Infrastructure tools that will allow me to build
better robots faster. So that's what I'm doing today.

The ``true test'' of my faith in my robotics abilities has
finally arrived.

A little background - I've been working on the Robocities
concept (the concept of having multiple little robots
construct a place they can ``call their own'' out of foam)
and I have created a prototype bricklayer that will be a
little slow but should work. The goal of this project is
to introduce a book and a web page that will inspire
advanced robotics hobbyists to build their own cities.

With this in mind I've opted to order the full complement
of prototype boards for 10 controller sets - a total cost
of $4,500 - which, in addition to some of the boards I
already have, will be used to control 7 robots 4
infrastructure projects, and 1 user/computer interface. I
estimate I'll need about another $2,000 to begin to raise
the cities and to complete the infrastructure projects.

Normally I would simply stretch this out over the next 3
years or so and gradually get it done. But the taxes on
our new home just shot up another $350 a month, and my
monthly cash outlay has now exceeded my cash intake. So
now I have an extreme need to make more money, which
frankly, I doubt I'm going to get through mobile robotics
at this time. So that means I'm going to have to either
work two jobs, or get a better job, either way robotics
time is going to get shelved fairly soon.

So this is it. I've opted to extend myself as far as I can
go financially to get this robotics project together and
out to the community, and after this, I don't know.

OK, college is finally over (after 16 years) and I've got
me one of them there pieces of paper. So now the question
is do I pursue robotics or do I get a real job (complete
with career)? After talking to my wife, I've determined
that I can always get a real job later, and for now I will
focus on robotics.

This is good because I made one of those
napkin contract (lower left
corner - I might have
been
drinking...) with Bruce Shapiro, a guy from my robotics
club
with deep affiliations with our local Science Museum,
indicating that if I complete my Robocities concept and he
will talk to the science museum people and find a space for
my creation.

I consider this a no-brainer since I was going
to
complete
this project anyway and even go so far as to write about
it.

I've already secured a lot of the proto-type
boards
I
want
to use and was working on the mechanical side of thing -
when disaster struck. A little detail I ignored - commonly
referred to as ``physics'' - informed me that the way I was
planning to build walls would produced more torque on a
particular motor then it was capable of handling.

Needless to say my carefully laid plans have
been
dashed on
the rocks below.

So for the next day or two I'll be working on
``plan
B''
which I hope works because ``plan C'' will reduce my
robot's
efficiency roughly in half.

I have two weeks left of school for my CS degree and then
it's over ...

My second wave of boards are on their way from Olimex.
It'll take me about a month to test them.

Predecessor is experiencing an ``operational pause'' due to
low funds (external factors sucked my robot budget dry).
I'm really not in the mood to switch projects in mid
stream, but hey, finances are finances. I take some
comfort in the knowledge that my other two major projects
integrate nicely with the technologies developed for
Predecessor. So I picked one of the other projects to work
on with the remainder of this years funds - Robocities.

Robocities is a pretty cool concept - robots build a city-
like structure using foam blocks. I did some extensive
work on this concept about three years ago, but lost
interest when my class load increased. Kept in the back of
my mind as one of the ``Big Three'' projects that I want to
write about, it will make a nice transitional project for
intermediate hobbyists and a good collective project for
universities who work on ``swarm'' robotics.

Since Robocities shares the same technologies as
Predecessor, a tremendous amount of work is already done.
Another plus is I can prove the concept by building one
robot - three machines gets the whole thing up and going.
I've ordered the motors for those machines, but I'm still
developing the sensor set I'll need to make the project
work.

In other news it looks like my robotics group TCRG is
experiencing some frustration at low turnout and project
stalls. I'm generally unable to attend meeting - lately
because of school - but I should be at the next one (in a
month) to share my project construction experiences. Maybe
I'll even have a small Robocity
Robot up and running.

I still need to order the parts, but I just sent the PCB
order for the second and hopefully last order before I
order all the boards for the platform (took long enough).
I decided I'm not ready to solidify the design so I'll be
ordering more prototyping boards instead of developing a
new task-specific board for the leg.

I also bought 2 more of those swell 58 lb. batteries. Damn
straight I'm going to put them on my robot, bringing the
robot weight in at 232 lbs for batteries alone. Heck,
that's almost a battlebot weight!

The DARPA
Grand Challenge confrencies are posting results from
the conference in the Forum. It looks like the judges
expect the ~250 mile course to be run in 6 - 10 hours by
the autonomous vehicles. I need 30 days
so...

I performed some experiments on the motors I have and came
up with some interesting results. Instead of a stall
torque of 50 lbs. at 12V 3.5 Amps, the stall is more like
100 lbs. at ~6 amps. This is good and bad. Good because
my robot is going to have plenty o' power to move around
(maybe even with a payload) bad because the L298 motor
driver I was planning to use ain't enough. My solution is
to make my own motor driver using FETs .

After blowing up a few "test units" (10 so far) learning to
work
with
them properly, I learned two things - A.) You've gotta tie
your gates down when you aren't using them. B.) Don't play
around with blowing up FETs, get a FET driver with a
high-side charge pump. I did some research and determined
the
HIP4081A fits my purposes
well - I also found out (via the internet) that a few of my TCRG hommies
have already gone down this path and are using the
HIP4081As now. I just placed an order with Newark for a
few drivers and I'm waiting for them now.

While playing the FET game, my supposedly good gel-cell
12V 17-AH batteries from Mendelson Electronics didn't
perform very well - like at all. Maybe I didn't take
proper care of them, maybe I got jacked, whatever. My next
move was to stop playing around with gel cells and get a
decent deep-cycle 12V marine battery. I found a
swell battery that put out 105 amps and at 58 lbs would
be
a
freakin' mongo lump in the middle of my `bot. I got 2 of
them and I'm going to put them both in the frame -
aesthetics
be damned.

I put (mostly) together what amounts to the new proto-type
leg and immediately determined I need bearings. I've been
hunting for them all day and finally stumbled across a bearing source on the net - I order a
couple pairs to play with. Along with the bearings I need
to lathe a decent aluminum axle (here is my future aluminum
source ) for each leg joint (I'm up to 5 per leg).
There have been many little changes to this leg design
along the
way and I expect there will be many more.

I came up with this modular method of prototyping boards I
was going to use across the board on my robot. I've
decided that would be a bad idea, and will only be using
prototype boards to figure out what the standard boards
will be. When I get it right I'll make a more economical
board to put in the robot.

This robot project is spinning off sub-projects out of
necessity. One thing I want to do is automate Kenneth
Maxon's oven-soldering method. Another thing I want to
do is morph my Sherline
lathe into a stand-alone lathe/mill (this is
mandatory). I'm trying not to lose focus and get
distracted by these sub-projects, but I might take a month
and bang them out. Luckily the same technologies used in
this robot project are easily morphed into these sub
projects. (If I say this often enough I might start to
believe it).

I hope you guys don't mind my embedding the links into
this entry - I sometimes use these entries to figure out
what the hell I was thinking when I did/bought whatever it
was that is in question. Someday I'll actually sit down
and do a web site -